1. Field of the Invention
The present invention relates to radio frequency (RF) monitoring systems, and more particularly to RF integrity monitoring systems for shielded enclosures.
2. Description of the Prior Art
Shielded enclosures are used when sensitive equipment or the like must be isolated from interference due to ambient electromagnetic radiation. An enclosure may also be used to confine radiation within the enclosure. When a shielded enclosure is first installed, the RF shielding effectiveness is at its maximum. After installation shielding effectiveness of the enclosure should be periodically tested to identify degradation of the shielded enclosure and RF energy leakage through the enclosure.
Integrity monitoring systems are used for testing the shielding performance of an enclosure to attenuate interference. Integrity monitoring systems typically include an RF transmitter with ar antenna on the outside of a shielded enclosure under test and a receiver with an antenna within the enclosure. Transmitted RF signals are detected by the receiver corresponding to the energy transmitted through the enclosure under test. However, extraneous, interference signals can be detected by the receiver to provide erroneous leakage indications for the shielded enclosure.
Another disadvantage of many known integrity monitoring systems is the lack of self-testing or self-diagnostics capability so that any hardware problems, such as in the receiver or the transmitter, tend to introduce inaccuracies.